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Add detailed comments to improve readability and explain key design decisions #217

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45 changes: 28 additions & 17 deletions pyperf/_process_time.py
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Original file line number Diff line number Diff line change
Expand Up @@ -22,26 +22,28 @@
import tempfile
import time

# Try importing resource module for memory usage tracking
try:
import resource
except ImportError:
resource = None


# Function to get maximum RSS (Resident Set Size) memory usage
def get_max_rss(*, children):
if resource is not None:
if children:
resource_type = resource.RUSAGE_CHILDREN
else:
resource_type = resource.RUSAGE_SELF
usage = resource.getrusage(resource_type)
# macOS returns bytes, Linux returns kilobytes
if sys.platform == 'darwin':
return usage.ru_maxrss
return usage.ru_maxrss * 1024
else:
return 0


# Merge two cProfile profiling statistics files
def merge_profile_stats_files(src, dst):
"""
Merging one existing pstats file into another.
Expand All @@ -52,26 +54,28 @@ def merge_profile_stats_files(src, dst):
dst_stats = pstats.Stats(dst)
dst_stats.add(src_stats)
dst_stats.dump_stats(dst)
os.unlink(src)
os.unlink(src) # Delete source after merging
else:
os.rename(src, dst)

os.rename(src, dst) # If no destination exists, just move source

# Benchmark a process by running it multiple times and collecting timing and memory data
def bench_process(loops, args, kw, profile_filename=None):
max_rss = 0
range_it = range(loops)
start_time = time.perf_counter()

# If profiling is requested, create a temporary profile output file
if profile_filename:
temp_profile_filename = tempfile.mktemp()
args = [args[0], "-m", "cProfile", "-o", temp_profile_filename] + args[1:]

for _ in range_it:
start_rss = get_max_rss(children=True)

# Start the external process
proc = subprocess.Popen(args, **kw)
with proc:
proc.wait()
proc.wait() # Wait for the process to complete

exitcode = proc.returncode
if exitcode != 0:
Expand All @@ -81,9 +85,11 @@ def bench_process(loops, args, kw, profile_filename=None):
os.unlink(temp_profile_filename)
sys.exit(exitcode)

# Update maximum observed memory usage
rss = get_max_rss(children=True) - start_rss
max_rss = max(max_rss, rss)

# Merge profiling results if profiling is enabled
if profile_filename:
merge_profile_stats_files(
temp_profile_filename, profile_filename
Expand All @@ -92,7 +98,7 @@ def bench_process(loops, args, kw, profile_filename=None):
dt = time.perf_counter() - start_time
return (dt, max_rss)


# Parse optional hook plugins from the command line arguments
def load_hooks(metadata):
hook_names = []
while "--hook" in sys.argv:
Expand All @@ -103,7 +109,7 @@ def load_hooks(metadata):
del sys.argv[hook_idx]

if len(hook_names):
# Only import pyperf if we know we have hooks
# Import hooks module only if hooks are requested
import pyperf._hooks

hook_managers = pyperf._hooks.instantiate_selected_hooks(hook_names)
Expand All @@ -113,31 +119,32 @@ def load_hooks(metadata):

return hook_managers


# Write benchmark results to stdout in a structured format
def write_data(dt, max_rss, metadata, out=sys.stdout):
# Write the data that is communicated back to the main orchestration process.
# It is three lines containing:
# - The runtime (in seconds)
# - max_rss (or -1, if not able to compute)
# - The metadata to add to the benchmark entry, as a JSON dictionary
# Three lines output:
# 1. Runtime (seconds)
# 2. Maximum RSS memory (or -1 if unavailable)
# 3. Metadata as a JSON dictionary
print(dt, file=out)
print(max_rss or -1, file=out)
json.dump(metadata, fp=out)
print(file=out)


# Main function for script execution
def main():
# Make sure that the pyperf module wasn't imported
# Prevent users from wrongly running this internal module via -m option
if 'pyperf' in sys.modules:
print("ERROR: don't run %s -m pyperf._process, run the .py script"
% os.path.basename(sys.executable))
sys.exit(1)

# Validate minimal argument count
if len(sys.argv) < 3:
print("Usage: %s %s loops program [arg1 arg2 ...] [--profile profile]"
% (os.path.basename(sys.executable), __file__))
sys.exit(1)

# Check if profiling is requested via command line
if "--profile" in sys.argv:
profile_idx = sys.argv.index("--profile")
profile_filename = sys.argv[profile_idx + 1]
Expand All @@ -149,10 +156,12 @@ def main():
metadata = {}
hook_managers = load_hooks(metadata)

# Extract the number of loops and the target command arguments
loops = int(sys.argv[1])
args = sys.argv[2:]

kw = {}
# Redirect stdin, stdout, stderr appropriately
if hasattr(subprocess, 'DEVNULL'):
devnull = None
kw['stdin'] = subprocess.DEVNULL
Expand All @@ -163,6 +172,7 @@ def main():
kw['stdout'] = devnull
kw['stderr'] = subprocess.STDOUT

# Handle multiple hooks cleanly using ExitStack
with contextlib.ExitStack() as stack:
for hook in hook_managers.values():
stack.enter_context(hook)
Expand All @@ -171,11 +181,12 @@ def main():
if devnull is not None:
devnull.close()

# Call hook teardown methods
for hook in hook_managers.values():
hook.teardown(metadata)

write_data(dt, max_rss, metadata)


# Entry point check
if __name__ == "__main__":
main()